4/21/2014 1 The Copernican Revolution Setting both the Earth and Society in Motion David Linton EIU Physics Department November 5, 2013 The Modern Picture of the Solar System A planet moves in an ellipse with the Sun at one focus. A planet moves fastest when closest to the Sun, slowest when furthest. A planet would travel in a straight line were there not a force to hold it to the Sun – this force is supplied by “Gravity” – an attraction between masses, and weakens with increasing distance. A planet’s axis is “fixed’ in space. (Orbital Period) 2 = (Semimajor Axis) 3 (This derives from the Law of Gravitation and Newton’s 3 Laws of Motion) Drawing an ellipse Focus Focus
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4/21/2014
1
The Copernican Revolution Setting both the Earth and Society in Motion
David Linton
EIU Physics Department
November 5, 2013
The Modern Picture of the Solar System
A planet moves in an ellipse with the Sun at one focus.
A planet moves fastest when closest to the Sun, slowest when furthest.
A planet would travel in a straight line were there not a force to hold it to the Sun – this force is supplied by “Gravity” – an attraction between masses, and weakens with increasing distance.
A planet’s axis is “fixed’ in space.
(Orbital Period)2 = (Semimajor Axis)3
(This derives from the Law of Gravitation and Newton’s 3 Laws of Motion)
Drawing an ellipse
Focus Focus
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Drawing an ellipse
Focus Focus
For a planetary orbit, one focus is unoccupied.
Drawing an ellipse
Sun
For a planetary orbit, one focus is unoccupied.
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Retrograde Motion – the Heliocentric View
Some Other Things We Now Know
Every planet beyond Earth has more than
one moon. Both planets closer to the Sun
than Earth have no moons.
Comets orbit the Sun also. They are dirty
icebergs (or icy dirtballs) orbiting along
extremely stretched-out (meaning, highly
eccentric) ellipses. Many of the comets we
see as they pass near the Sun take many
thousands of years to orbit one time.
Astronomy at Copernicus Birth
(1473)
Ancient Greek Philosophers held that Earth was
the center of Creation, that everything in the sky
must wheel in circles about us.
Circles were considered the perfect geometric
form, and the Greeks had felt the Heavens to be
perfect. Spheres and circles abound in the
depictions of Claudius Ptolemy, who assembled
the best summation of Greek Cosmology in
about 150 A.D.
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Astronomy at Copernicus’ Birth
(1473)
The astronomical heavens were also the
theological heavens. It was there that the gods
resided (when they weren’t involving
themselves in earthly matters).
If the heavens are perfect, then no change can
improve them. Therefore, changes (transitory
phenomena) that are observed overhead MUST
be nearby – in our atmosphere or no further
than the deferent of the Moon.
Astronomy at Copernicus’ Birth
(1473)
Thus, both meteors (quick bright flashes in the
night sky) and comets (slow-moving “hairy
stars”) were considered atmospheric
phenomena. Comets were especially feared.
Astronomy at Copernicus Birth
(1473)
Aristotle was the Greek Philosopher held in
highest regard. His contributions were in a
multitude of realms, not Astronomy alone. Many
later thinkers deferred to Aristotle, in what some
have called a centuries-long inferiority complex.
Ptolemy’s version of the Geocentric Theory was
considered to be consistent with Christian
theology, and was eventually accepted as an
article of faith by the Roman Catholic Church.
Astronomy at Copernicus Birth
(1473)
Hence, to question geocentrism was to question
the authority of the Church – and any modern
version of science requires a questioning
approach to nature.
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Those who believe the Sun revolves around the Earth:
U.S. 20% (another 9% claimed not to know)
Britain 16%
Germany 18%
Russia 32%
Notes:
1. In the U.S., geocentric belief is usually associated with a literal belief in the Bible.
2. Quoted results are from polls conducted in the last 20 years.
Syntaxis Mathematica (Almagest) The Seven planets
were :
Moon
Mercury
Venus
Sun
Mars
Jupiter
Saturn
It is from these
wanderers that we
derive names for
the days of the
week:
Sunday
Moonday
Saturnday, etc.
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The 3 E’s of the Geocentric Theory
of Claudius Ptolemy
The Epicycle
The Eccentric
The Equant
The Epicycle
The Eccentric – Earth is Not at ‘C’
The Equant
The planet moves
uniformly around
the equant ‘M’.
Each segment of
the circle is traversed
in an equal amount of
time. So the planet
speeds up as it gets
further from ‘M’.
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Epicycle, Eccentric, & Equant Combined
So, despite its name, the
Geocentric Theory did
NOT place the Earth at
the very center. Ptolemy
placed Earth as close to
the center as he could,
while still modeling the
apparent motions of the 7
planets with the use of circles
alone.
Epicycle, Eccentric, & Equant Combined
Each planet had its own
set of circles. In the
words of Jacob
Bronowski, the
problem was that
the heavens
should require ONE
machinery, not seven.
Copernicus Has Been Criticized
In 1503 & 1504, Mars, Jupiter &
Saturn converged in Gemini
M J S
Sept 7, 1503
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Sept 21, 1503 Oct 6, 1503
Nov 19, 1503 Dec 29, 1503
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Feb 4, 1504 Mar 8, 1504
Mar 8, 1504
Ptolemy’s theory predicted Mars to be 2° further
West, and Saturn would be 1.5° further East. A Heliocentric Universe Must Be Much Larger